Electronic systems and circuits have made a significant contribution towards the advancement of modern society and are utilized in a number of applications to achieve advantageous results. Numerous electronic technologies such as digital computers, calculators, audio devices, video equipment, and telephone systems facilitate increased productivity and cost reduction in analyzing and communicating data, ideas and trends in most areas of business, science, education and entertainment. Frequently, these activities often involve the presentation of various graphics information on a display.
Graphics applications associated with the display presentations can have different characteristics and features. For example, graphics applications can have different processing requirements, different quality features, involve different levels of complexity, and so on. A system may include multiple graphics processing units and the graphics processing units can also have different processing capabilities and characteristics. In addition, control software and hardware for each processor may be entirely different (e.g., processors manufactured by different vendors, etc.) and not able to be controlled identically. Furthermore, displays typically can only handle input from one graphics processing unit at a time and often have particular interface requirements. For example, if signaling is not performed correctly damage to the panel may result, or the user may observe disturbing visual artifacts, or the panel controller may force a failsafe shutdown.
Ensuring the timing requirements are met when changing between active graphics processing units can be complicated and complex. Before a transition occurs one GPU is driving the LVDS and there is an extremely small chance that signals from the GPU are aligned with another GPU, creating flickering and substantial delays while a Panels Timing Controller (TCON) resynchronizes with the second source. For example, when a switch occurs one GPU may be at the end of a raster scan while the other is at the beginning. Displays typically have panel power sequencing specifications that indicate signal activation timing requirements. For example, the standards panel working group (SPWG) indicates general mechanical and interface specifications (e.g., SPWG spec, http://www.spwg.org) for displays used in note book computers. Detrimental impacts to images and the display itself can occur if timing requirements are not adhered to. In addition, if the panel power sequencing specifications are not adhered to the TCON may take multiple frames until it re-acquires the vertical sync such as indicated by the assertion of VSync signal, or the de-assertion of Display Enable, whereupon it can begin to re-synchronize to the second GPU's signal. If the mis-sync lasts too long then the TCON can misinterpret the condition as a loss of timing and then enter Fail-Safe mode wherein the LCD is safely shutdown and the panel must be powered-off and on before it will re-enable displays.